Can't run windows update, computer is slow, Pop-ups, vundo virus?

I am having a very hard time with my computer right now. Well first off, a couple of days ago my computer started to run very slowly. After that, I would notice that my Windows Update would automatically turn off at startup. I have been trying to turn it back on, but I cannot and I receive and error mssg. (1058). My Symantec Antivirus would also turnoff on its own after my computer as been on a few minutes. Also, while trying to browse on IE or Firefox, I receive a lot of pop-up advertisements (mostly on anti-spyware software). Lastly, from time to time my computer will just completely freeze up.

I have an Acer Travelmate 8100 that runs Win. Xp Professional.
After doing some research on the internet, it seems like I might have the vundo virsus...but i'm not completely sure of that. I have tried removing all threats by using Ad-aware, Spybot, and countless virus scans using Symantec Anti-virus...but I still have no success in removing whatever the infection is...I still have the problems.

If ANYBODY knows how I could solve these problems, please help...I would greatly appreciate it! (if anymore information on my situation is needed...please let me know)